A PBM audit that reviews only a sample of prescriptions can turn into a much larger recoupment demand once the pharmacy benefit manager applies extrapolation, the statistical practice of projecting a sample's error rate across a larger group of claims that were not reviewed. OptumRx's 2026 pharmacy provider manual, for one, reserves the right to extrapolate audit sample exceptions against the entire population under audit when it determines that cumulative errors rise to the level of negligence or fraud, waste and abuse, subject to applicable law. Challenging that methodology, not only the underlying claims, is one way to contest the amount demanded.
How PBM Extrapolation Inflates a Recoupment Demand
In an extrapolated audit, the auditor reviews a sample of claims and projects the errors it finds across claims it did not review. The errors found in the sample, not a review of each claim, then set the amount demanded for the whole population under audit. The Federal Judicial Center's Reference Guide on Statistics points to what makes an estimate of that kind reliable: a probability sample, drawn by a chance mechanism that leaves no room for selection bias, and attention to sample size, because chance error is smaller for larger samples. The guide adds that, whenever possible, an estimate should be accompanied by its standard error. A demand that states only a dollar figure, without the sampling frame, the sample size or the standard error, leaves the pharmacy no way to evaluate whether the extrapolation is sound.
State Laws Restricting Extrapolation Audits
Some states have moved to limit or ban the practice. The National Academy for State Health Policy is the source a May 2026 issue brief from the Medicaid and CHIP Payment and Access Commission cites for its statement that all 50 states have passed some form of legislation regulating PBMs. Michigan's Pharmacy Benefit Manager Licensure and Regulation Act bars a carrier or PBM from conducting an extrapolation audit, defined in the statute as using a sample to estimate results across claims never reviewed, except where a federal program requires it. Texas goes further: Insurance Code Section 1369.259 prohibits a PBM from using extrapolation to complete an audit at all, requires any recoupment to reflect the actual overpayment identified, and bars a PBM from making an extrapolation audit a condition of network participation. The National Community Pharmacists Association keeps its own page on PBM reform legislation. Minnesota is a third example: section 62W.09 of its statutes bars a PBM or its representative from using extrapolation to calculate a recoupment or penalty unless state or federal law or regulations require it, and the section does not apply to an investigative audit that involves suspected fraud, willful misrepresentation or abuse, or to an audit completed by Minnesota health care programs. Whether extrapolation is available in a given audit depends on which statute applies and what it excepts, so the first question in any extrapolated PBM audit is whether state law permits the projection at all.
The Statistical Objections That Reduce Demands
Where extrapolation is legally available, the demand is still only as strong as the sampling behind it. Counsel can request the auditor's underlying workpapers, the sample frame, the randomization method, the confidence and precision level, and the standard error, then challenge the projection on specific grounds: a sample too small to support the stated confidence level, a sample drawn non-randomly from claims already flagged as likely errors, an error rate that treats immaterial clerical mistakes the same as substantive overpayments, or a claim universe that improperly sweeps in claims outside the audited category. A successful objection can invalidate the extrapolation, leaving the claims the auditor actually reviewed, or force a recalculation of the extrapolated figure in the audit appeal.
An extrapolated demand is an estimate, and it is only as reliable as the sample behind it: whenever possible, an estimate should be accompanied by its standard error.
Why Early Legal Counsel Is Critical
It is critical that pharmacies promptly retain experienced healthcare defense counsel upon receiving a PBM audit notice or an extrapolated recoupment demand. Early legal intervention can protect the pharmacy's rights, request the sampling workpapers before the response window narrows, identify which state's audit statute applies, and raise statistical and clerical-error objections while the audit appeal is still open. Delaying counsel until after the extrapolated demand is finalized can significantly affect the outcome.
How Health Law Alliance Can Help
Health Law Alliance represents pharmacies nationwide in audits by OptumRx, CVS Caremark, Express Scripts, Prime Therapeutics, Humana and other PBMs, including challenges to audit findings, methodology and extrapolated recoupments. For related reading, see Navitus Audits: What Pharmacies Should Know and OptumRx Audit Defense: What Pharmacies Should Expect, or, on what happens when an audit escalates, How PBM Audit Findings Escalate to Network Termination. If your pharmacy has received an extrapolated recoupment demand and is facing possible network termination, contact our PBM audit defense team for a free, confidential consultation.
